In many mining operations, digging or breakout forces in the neighborhood of 200,000 pounds are required, and at the same time, for practical utilization, the excavated material must be removed at rates approaching 100 tons per hour. With existent equipment these two practical requirements are not achieved. For example, mechanical devices such as backhoes and front end loaders could possibly deliver the requisite forces but have not the capacity to remove the material in such large quantities. On the other hand, certain boom-mounted rotary heads can remove the material at adequate rates but are not only incapable of delivering the requisite forces but also establish force components which tend to move the entire machine sideways so as to render its operation impractical.
Both problems are aggravated when one wishes to perform the excavating and conveying operation in a mining tunnel whose lateral dimensions conventionally are no more than six feet high and five feet wide, since the mentioned breakout or digging forces are sufficient to lift or transversely displace the mobile carrier for the equipment.